This application claims priority under 35 U.S.C. §119 to Japanese Patent Application No. 2007-234699 filed on Sep. 10, 2007 and Japanese Patent Application No. 2007-265237 filed on Oct. 11, 2007, the entire disclosure of which is incorporated herein by reference in its entirety.
1. Field of the Invention
The present invention relates to coating method of building board having convexoconcave in surface. More specifically, the present invention relates to coating method of building board coats the whole surface of the building board and the whole edge of the building board enough with coating while transporting the building board.
2. Description of the Related Art
The following description sets forth the inventor's knowledge of related art and problems therein and should not be construed as an admission of knowledge in the prior art.
In general, a design by convexoconcave is given in surface of building board, and it is tended to improve a good appearance. And it is usual to coat surface having convexoconcave and edge with coating for improving an appearance more and controlling alteration of physical property such as dimension by water absorption in the building board. In addition, edge of building board has shiplap portion to install the building board with another building board disposed by top and bottom and right and left.
An example of building board is shown in FIG. 15. Building board A shown by FIG. 15 has a lot of convex portions A7 of block which are protruded in surface, so that building board A has convexoconcave in surface by a lot of convex portions A7. In addition, edge comprises an edge having edge side face A5, an edge having edge side face A6, an edge having upper shiplap portion A1 and edge side face A2, and an edge having lower shiplap portion A3 and edge side face A4. Upper shiplap portion A1 is formed on an edge of building board A by cutting from a back side of building board A partly, and upper shiplap portion A1 is formed on edge whole area by making notch on the edge whole area. In addition, lower shiplap portion A3 is formed on another edge of building board A which is different from upper shiplap portion A1 of building board A by cutting from a front side of building board A partly, and lower shiplap portion A3 is formed on edge whole area by making notch on the edge whole area. In addition, notch of upper shiplap portion A1 is formed more greatly than notch of lower shiplap portion A3. Therefore, when building board A is attached in external wall of building, upper shiplap portion A1 is able to engage with lower shiplap portion of other building board, and lower shiplap portion A3 is able to engage with upper shiplap portion of another building board, so that external wall of building can be comprised by building boards.
As method to coat with coating for described above building board, there are a brushing method, a roll coater method, a spraying method and a curtain coater method.
In the brushing method, building board is coated with coating by touching a brush having coating.
In the brushing method of building board having shiplap portion in edge, the edge and surface of the building board are coated with coating by touching a brush having coating, but it is difficult to touch the brush to the edge and the surface of building board in uniformity and to touch while transporting the building board. In addition, it is more difficult in building board of large size and/or building board having a design by convexoconcave in surface. Therefore, there is danger that a portion where coating is insufficient occurs, so that it influences physical property and appearance of building board. Moreover, the brush is worn by touching building board directly, so that the brush is easy to be transformed, and a replacement is necessary immediately.
In the roll coater method, it makes coating in surface of roll by soaking one part in surface of rotating roll, and the coating are moved to building board via the roll. In the roll coater method, coating in surface of roll are moved to a portion of building board which the roll touched, so that the coating is able to coat the building board while transporting the building board. In addition, if surface of building board is smooth, coating moves in the surface, and the surface of building board is coated with coating enough. However, in building board having a design by convexoconcave in surface, concave portion of the building board cannot touch in roll, so that coating cannot be moved into the concave portion of building board. Therefore, there is danger that a portion where coating is insufficient occurs, so that it influences physical property and appearance of building board. In addition, edge having shiplap portion is convexoconcave, so that the edge cannot touch with the roll in the whole, and coating cannot be moved into the edge. Therefore, there is danger that a portion where coating is insufficient occurs, so that it influences physical property and appearance of building board. Furthermore, surface of building board and edge having shiplap portion cannot be coated with coating at the same time. And when coating is circulated, debris of building board tends to be contaminated, and the debris attaches to roll, so that there is danger that a portion where coating is insufficient occurs. In addition, a condition of coating is affected by viscosity of coating to use, so that viscosity of coating must be controlled.
In the spraying method, building board is coated with coating by spraying coating from a apical nozzle. In the spraying method, coating is sprayed in surface of building board, so that the coating is able to coat the building board having a design by convexoconcave in surface while transporting the building board. However, coating condition of concave is different from coating condition of convexity, so that there is danger such as a portion where coating is insufficient occurs in slope of convexoconcave and/or a portion where coating is gathered occurs in concavity. Therefore, it influences physical property and appearance of building board.
In addition, there is a method to spray coating on towards an edge of building board from the diagonal lower position to coat the edge of building board having shiplap portion. However, coating is sprayed from the lower position, so that there is danger such as adhesion of coating is bad and/or spray is easy to be clogged up. Alternatively, there is other method to spray coating on shiplap portion by inverting building board. However, it is necessary for inverting building board in the method, so that it is inefficient. And there is danger that coating does not reach to the depths of shiplap portion by shape of the shiplap portion, and a portion where coating is insufficient occurs.
Furthermore, when coating is circulated, debris of building board tends to be contaminated, and a apical nozzle of spray is clogged with the debris, so that there is danger that a portion where coating is insufficient occurs. At Japanese Patent Laid-Open No. 2003-1155, a method that a rate of flow of coating supplied in nozzle of spray is measured with flowmeter and is managed is disclosed. However, the method detects inconvenience such as clog of nozzle quickly, clog of nozzle cannot be prevented. In addition, bubble is easy to occur in coating because a spraying method is to pressurize the coating and to blow the coating, so that an antifoaming agent is necessary in large quantities. As the side effect, there is danger such as harmful effect to formability of coating film and/or harmful effect to adhesion of other coating by the coating repelling in the next process where other coating is coated. In addition, a condition of coating is affected by viscosity of coating to use, so that viscosity of coating must be controlled.
In the curtain coater method, it makes curtain of coating by overflowing from a side wall of coating storage, and building board is coated with coating by passing through the curtain of coating. If surface of building board is smooth, the curtain coater method can coat the surface of building board with coating uniformly. However, amount of coating to the surface of building board by the curtain coater method is only around 120 g/m2. Therefore, in building board having convexoconcave in surface, coating can coat slope of convexoconcave disposed in a travelling direction side of transportation, but coating can not coat slope of convexoconcave disposed in a reverse side to travelling direction of transportation, and there is danger that a portion where coating is insufficient occurs, so that it influences physical property and appearance of the building board.
In addition, for coating edge of building board having shiplap portion, the building board is inverted and passes through the curtain of coating. However, it is necessary for inverting the building board in the method, so that it is inefficient. And there is danger that coating does not reach to the depths of shiplap portion by shape of the shiplap portion, and a portion where coating is insufficient occurs.
Furthermore, when coating is circulated, bubble is easy to occur in coating, and curtain of coating breaks off, so that there is danger that a portion where coating is insufficient occurs. In addition, debris of building board tends to be contaminated, and the side wall of coating storage is clogged with the debris, so that there is danger that a portion where coating is insufficient occurs.